Panel Discussion of the Nuclear Fusion Net Gain of Energy In and Out of the Target

LLNL’s experiment surpassed the fusion threshold by delivering 2.05 megajoules (MJ) of energy to the target, resulting in 3.15 MJ of fusion energy output, demonstrating for the first time a most fundamental science basis for inertial fusion energy (IFE). Many advanced science and technology developments are still needed to achieve simple, affordable IFE to power homes and businesses, and DOE is currently restarting a broad-based, coordinated IFE program in the United States.

If captured with 100% efficiency, the 1.05 Megajoules is enough to power a hair dryer for 30 minutes. It is about 280 watts.

The Net Gain is the energy hitting the pellet target and the energy coming out of the target.

17 thoughts on “Panel Discussion of the Nuclear Fusion Net Gain of Energy In and Out of the Target”

  1. The most encouraging aspect of this is the jump in power. September’s shot was 70% energy back or something, this time 120%.

    That’s not slowly creeping up on unity. That’s tweaking a parameter and suddenly it works. (For small values of “works”)

    And if you can double the yield with one tweak, I’d be very surprised if there wasn’t a lot more yield available. A factor of 2? Very likely. A factor of 5? Not impossible. Our panel above was dropping hints that they have ideas about how to go forward on the design.

    Then we’d have a yield of 6 or 7. Now you’ve got enough excess energy to try to have another stage or two.

    Then? Well we’ve got the cloud of vapourized gold to absorb the energy, run the liquid gold through a heat exchanger and start boiling our really big kettle.

  2. Is there interdisciplinary connection to industrial groups discussing what real reactor design could/will be usable for extracting and converting alpha particles and neutrons kinetic energy for grid like distribution?

  3. Only 4% of the deuterium-tritium fuel burned in the fusion reaction, suggesting plenty of room for improvement.

    So using more efficient lasers and more powerful ones, different capsule setup,… way higher gain could be achieved.

  4. I will not downplay the achievement of others to lift my personal ego.

    They proved to the naysayers that:
    – Ignition is possible.
    – They got more energy out of the reaction that was needed to start it. It is proven.

    So others can expect, that that is possible, can be done and can pursue it.

    They have taken 300 MJ out of the grid for that experiment.
    Some would argue that that is not net gain. That is understandable, but some of NIF tech dates back even to 80s, It is an old facility. NIF lasers are very ineffective. Modern lasers would be up till 40 times more effective. So we can get into about 10 MJ range with modern laser tech,..

    The point of experiment was not to produce commercial fusion. It was to prove, that if the concept works, if it is even possible and find optimal ways to do it. They proved it. Laser pulse was 2.05 MJ and they got more energy out that was needed to begin the ignition, 3.15 MJ. Prehistoric man used spark to light a fire and got more energy out that was put into.

    Now since modern laser tech is much more efficient and peak laser power is increasing roughly by a factor of 1000 for every 10 years it is job for non naysayers to find the solutions and try to do it in practical sense. They can build upon on what was proven and how it was done.

  5. There really is no upside to 80% of the D-T yield being neutrons with such a small reaction control volume…. that’s the Creators way of saying: use fission.

  6. Gosh. It only takes a 7.5 billion dollar machine to make 1.1 / 3.6 = 1/3 of a kilowatt-hour of over-unity thermal / x-ray / energetic nucleons energy. Doesn’t feel like a watershed moment … you know, like investing one’s life savings into the just-around-the-corner gigawatt Mr. Fusion reactors.

    I know that this comment is both a lampooning … and a cynical take. My apologies. The LLNL result is actually a marvelous thing, technically. As Combinatorics has mentioned elsewhere, the idea of popping several hundred of these hohlrahm fusors off … per second … and blasting the reaction chamber with kilograms of beautiful gold plasma, is definitely going to present some cleanup issues. After minutes of operation. This is a problem.

    Also, at the present, NECESSARILY, the reaction production energies are basically mostly thermal. Or converting-to-thermal on the millisecond timescale. So… using 19th century physics, that thermal energy needs converting at perhaps 35% to 45% efficiency to electrical (or mechanical) by the usual methods (steam!).

    Let me distill this to the essential real-world break even consideration: at 35% conversion efficiency (“all in”), the COP needs to be ‘3’ just to keep such a scheme running … and not outputting a single kilowatt-hour of useful juice to the grid. Realistically, it needs a COP of ‘10’ at least, and more realistically, 25 to 50 to make fusion-produced energy a juicy target for commercial investment.

    So there’s the goalpost. When

    [1] COP hits at least 10
    [2] Gross production hits at least ‘high megawatts’
    [3] Production-of-machine costs don’t exceed $1000 per kW (net output)

    Then fusion can shoe-in as a clean power producing alternative to cutting down forests to fuel the so-called green energy reactors.


    • NIF is a science experiment that met its stated goal, albeit a decade late. The announcement of this success is taking flack from many with a sentiment I don’t share. I think it’s great that the teller-ulam device was finally demonstrated without a fission bomb driver. I can only imagine how sensitive the physics are for lack of a really clobbering driver combined with whatever manufacturing variations may exist in such small targets. Considering the best LEDs have 15-25% luminous efficiency, the COP does indeed need to be quite high to make this work. If they get this working repeatably with more complete fuel utilization, they can move on to cascading to larger driven stages. With eventual transition to a solid state driver, deuterium/lithium, and staged implosion, there is a success path here for large scale thermal machines. I’m sure there are substitutes for gold. Do I think this will happen? No. Do I think we should pursue it as a nation? Maybe, at current funding levels. It is not just my estimation that none of the fusion concepts in development will amount to anything as useful, reliable or economical as Diablo Canyon for terrestrial power generation – ever.

      • Your reply is much nicer than my comment … and I basically agree with you. What isn’t clear though is whether this tech could really conceivably ever be cobbled together as a staged device … one lil’ bomb triggering a bigger lil’ bomb, and that a third way larger but still quite mini bomb.

        The present device works (as in ‘at all’) because of exquisitely well-focused and tightly timed terawatt laser beams hitting both sides (important) of the hohlrahm in just such a way to compress and contain the fuel pellet for nanoseconds … enough.

        As you and I both have obviously read about and understand the Teller-Ulam full-on-bomb tech … which basically utilizes a modest fission bomb’s nanosecond-scale pulse of gamma and hard X-ray energy, along with an ellipsoid shaped containment vessel, to focus that torrent of energy onto the fusion target, compressing it radically and heating too … I am having a hard time figuring out how a containable burst reaction could be contained and focused well enough onto a chain-of-hohlrahms to multiply energy to the gigajoule level. Seems like quite a stretch. But who knows. Maybe do-able.

        Thank you again, and may the future look bright!!!

      • The physics is positively awesome. I dislike how it is being presented by the technically illiterate media who are positioning this as some kind of energy source and by our Energy Secretary babbling pablum by describing fusion as an inclusive energy source. NIF would never be able to compete with FOAK Gen III+ reactors on cost and so it is a dead end.

        And the Gold hohlraum isn’t the issue so much as any hohlraum will turn to plasma and coat the walls. This will very quickly diffuse the UV laser light coming in and make the machine useless. I will say that the prospect of hundred tons of molten, radioactive Gold at the bottom of the reactor does at least check the requisite Steampunk boxes.

        • I’m not sure how condensed metal on the walls would interfere with a laser more than the locally vaporizing hohlraum, which has been overcome in the NIF experiment, but I think we have different mental models for extending the technology to make a thermal machine.

          I imagine you believe repetition rate is important because your machine would be on a scale of the general atomics or tri-alpha designs, which implode little fart puffs of DT.

          In my mental model there is a 22nd century vintage diode laser array synced to the picosecond irradiating a 2+staged ‘package’ within an ablation-expansion/pressure chamber of ‘civil engineering scale’. The ‘package’ would be a sheet steel case (tin can) with targets suspended in aerogel, arranged with symmetry around the laser driven cavity – probably with some obstruction of the direct line of sight between cavities.

          How to design the expansion chamber and get 4GW out of it? Well isn’t that is an interesting problem, especially considering it would be full of fallout, but that is no different from any other concept using D-T. I figure all the complexity of ICF is in the laser, which will have other applications (death ray), and the target design, which will give stockpile stewards something juicy to noodle on for years to come…

          None of this is practical, or in compliance with the test-ban treaty, but yield has to absolutely dwarf input to make fusion work economically. Repetition rate becomes less important as gain increases. Complexity also works against economics. Inertial confinement fusion is all around us in the cosmos… that is the way to do it.

      • “Current funding levels” is somewhat besides the point. This is getting all the politicians and public to sit up and take notice.

        I’d be VERY surprised if funding didn’t get a serious boost.

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